Cybercriminals were quick to integrate a newly released exploit for a Java vulnerability patched in June into a tool used to launch mass attacks against users, an independent malware researcher warned.

The exploit targets a critical vulnerability identified as CVE-2013-2465 that affects all Java versions older than Java 7 Update 25 and can enable remote code execution. The vulnerability was patched by Oracle in its June Critical Patch Update for Java.

The exploit was released Monday by security research group Packet Storm Security, which originally acquired it through its bug bounty program as a zero-day exploit -- an exploit for an unpatched vulnerability -- from a researcher whose name was not disclosed. Packet Storm publishes the exploits it acquires 60 days after it receives them, with permission from their authors, so other security professionals can use them to perform penetration tests and security risk assessments.

Two days after its release, the CVE-2013-2465 exploit was already integrated into so-called exploit kits, attack tools that infect computers with malware by exploiting vulnerabilities in outdated software when users visit compromised websites.

An independent malware researcher who uses the online alias Kafeine found a live installation of the Styx exploit kit, previously known as Kein, that is using the exploit.

From an attacker's perspective the exploit for CVE-2013-2465 is better than the exploit for CVE-2013-2460, another Java vulnerability also patched in June, that was recently integrated into a different attack toolkit called the Private Exploit Pack, Kafeine said Thursday in a blog post. That's because CVE-2013-2465 affects both Java 7 and Java 6 installations, while CVE-2013-2460 only affects Java 7, he said.

Oracle ended its public support for Java 6 in April and will no longer release security updates for it to all users. Despite this, Java 6 is still widely used, especially in enterprise environments.

A recent study by security firm Bit9 showed that more than 80 percent of Java-enabled enterprise computers have Java 6 installed on them. The most widely deployed Java version on those systems was Java 6 Update 20.

The latest publicly available version of Java 6 is Java 6 Update 45, which is also affected by CVE-2013-2465. The vulnerability was patched in Java 6 Update 51, but this version is only available to users who have extended support contracts with Oracle.

The fact that an exploit for CVE-2013-2465 is publicly available and has already been integrated in mass attack toolkits suggests that this vulnerability will soon see widespread exploitation. Users who have yet to upgrade to Java 7 Update 25 might want to do so as soon as possible.

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